Hello guys so the tires on my car now are low profile 225/40/18 both front and back.

my front all season tires needs to be replaced soon and my back tires are new snow tires that i got last season.

is it ok to mix and match tires? cause for the replacement i don't want to get low profile tires anymore and go with a bigger sidewall. If i get the new front tires of 225/45/18 and my backs are still 225/40/18 will this switch damage my axles?

Yeah, the reason people tell you not to do it is because AWD cars don't like it--the center diff will constantly feel as if there's slippage going on because the front and rear wheels aren't spinning at the same speed. Since your car is FWD, there's no center diff, and thus no physical connection between the front and rear wheels of the car.

Your mechanic was full of shit, yes, unless he thought you were putting different tires on the left and right. Then he'd be right.

As for what costs more, it all depends on the tire. You can't just generalize that 'low-profile' tires cost more. Find the size you want, check the prices, buy what you can afford that has decent reviews.

Having different sized tires on a modern car can actually mess with a number of systems. ABS is a big one, and by extension, traction control. Depending on the manufacturer and year of the car, it may also mess with the TPMS system if it does calculation rotationally as opposed to by actual pressure.